Dr. Xianming Chen, USDA-ARS plant pathologist, released his first forecast of the 2024 crop year on January 8, and is predicting stripe rust severity to be severe (40-60% yield loss for a highly susceptible experimental variety). These predictions are based on air temperatures in November and December and translate to yield loss of 0-27% for currently grown commercial winter wheat varieties, depending on susceptibility. This forecast is much worse than the January 2023 forecast of 0-15% yield loss for commercial varieties primarily because of the very mild temperatures in November and December 2023 compared to the same period in 2022. Note that this prediction does not factor in the amount of stripe rust present in Fall 2023, nor does it reflect the cold temperatures that occurred during mid-January and resulted in widespread winter damage to some varieties.
Although this forecast sounds dire, there is a long way to go to harvest and much we don’t know. That said, the current long-range weather forecast calls for mild temperatures, which are favorable to stripe rust survival and development. Dr. Chen’s March predictions are typically more accurate because we will have a better idea of late winter temperatures and their impact on survival of the stripe rust fungus and will likely have visual survey data on presence of stripe rust. This year, we will also have a better handle on the impact of the mid-January cold temperatures on winter wheat and rust survival, so stay tuned.
Given this current prediction, I encourage you to take a look at spring wheat stripe rust resistance variety ratings in the WSU Variety Selection Tool (also available in Dr. Chen’s forecast and the 2022 WSCIA Certified Seed Buying Guide) as you are considering the best spring wheat varieties to plant and/or your fungicide program for this spring. As always, we encourage you to select the most resistant variety possible, preferably rated 1-4, for your production area.
Stay tuned for more rust updates as conditions change. In the meantime, you can find additional information about stripe rust, including photos showing rust percentage under the Foliar Fungal Diseases and updated rust ratings for winter and spring wheat varieties in my presentation “Diagnosing and Managing Diseases of Wheat” from the 2023 Wheat Academy.
For questions or comments, contact Tim Murray via email at tim.murray@wsu.edu, via phone at (509) 335-7515, or by following him on Twitter @WSUWheatDoc.